In recent years, devices such as liquid crystal TVs (television sets) have been becoming larger. Many display devices for use in such liquid crystal display TVs etc. employ a backlight constituted by a direct surface light source device. According to such a surface light source device, light sources can be arranged all over the back surface of a liquid crystal panel, and thus high luminance is easily achieved even in the case where the liquid crystal panel has a large screen.
Many of such backlights include, as a light source, solid-state light-emitting elements such as LEDs, for the purpose of reducing the thickness of the display devices and also reducing electric power consumption.
FIG. 29 is a cross-sectional view schematically illustrating a configuration of a liquid crystal display device 300 which includes a backlight 330 constituted by a direct surface light source device.
As illustrated in FIG. 29, the backlight 330 includes a plurality of LEDs 331 which are covered with lens caps (not illustrated). The LEDs 331 are arranged, for example, in a plurality of lines in a matrix manner or in a zigzag pattern on a backlight substrate (not illustrated) which has substantially the same shape as a liquid crystal panel 310.
The backlight substrate further has, for example on the entire surface thereof, a reflecting member 332 such as a reflecting sheet so that light is more efficiently reflected at the backlight substrate.
Note that, as described above, each of the LEDs 331 is covered with a lens cap (not illustrated), and light emitted from each of the LEDs 331 passes through the lens cap and illuminates a surface (which is to be irradiated by the light) of the liquid crystal panel 310 (such an object irradiated with light is hereinafter referred to as an irradiation target). Note, however, that FIG. 29 does not illustrate the lens cap for simplification.
Furthermore, between the LEDs 331 and the liquid crystal panel 310, there is provided a diffusing plate 320 for diffusing light, for the purpose of (i) preventing light and dark luminance patterns (i.e., spots of LEDs) due to bright lines attributed to the LEDs 331 and (ii) suppressing in-plane unevenness of luminance.
Note that, in FIG. 29, the arrow represents the path of light emitted from the backlight 330.
A known example of such a direct backlight 330 including the LEDs 331 as light sources is a flat surface light source described in Patent Literature 1.
FIG. 28 is a perspective view schematically illustrating a flat surface light source 400 described in Patent Literature 1.
As illustrated in FIG. 28, the flat surface light source 400 described in Patent Literature 1 includes (i) a plurality of LED chips 401 arranged on a flat surface and (ii) a microlens array 411 provided so that its microlenses correspond to light emitted from the respective plurality of LED chips 401.
In Patent Literature 1, a front substrate 412, on which the microlens array 411 (which serves as lens caps) is provided so that its microlenses correspond to the respective plurality of LED chips 401, is provided on a backside substrate 402 on which the LED chips 401 are arranged. With this configuration, light emitted from the LED chips 401 is collimated when passing through the microlens array 411, and collimated light is emitted to the outside.